topic Re: Modified projection failing to draw in ArcGIS Pro Questions

Modified projection failing to draw

AmyRock1 — Tue, 30 Jan 2018 20:17:42 GMT

Modifying a projection in ArcPro, and it fails to draw.

Using South America Lambert Conformal Conic and changing the central meridian. Coordinates at the bottom of the map window work fine in the original, after modification, latitude coordinates change to <Null> ºN (longitude still works fine), regardless of where you move the mouse. Thoughts?

Original:

Latitude Of Origin -32.0
Standard Parallel 2 -42.0
Standard Parallel 1 -5.0
Central Meridian -60.0
False Northing 0.0
False Easting 0.0
Linear Unit Meter (1.0)
Authority Esri
WKID 102015
Projection Lambert Conformal Conic
Projected Coordinate System South America Lambert Conformal Conic

Modified:

Latitude Of Origin -32.0
Scale Factor 0.0
Standard Parallel 2 -42.0
Standard Parallel 1 -5.0
Central Meridian -69.0
False Northing 0.0
False Easting 0.0
Linear Unit Meter (1.0)
Authority
WKID -1
Projection Lambert Conformal Conic
Projected Coordinate System South America Lambert Conformal Conic 1

Re: Modified projection failing to draw

AdrianWelsh — Wed, 31 Jan 2018 21:53:00 GMT

Amy,

Hmmm, that is pretty strange. When I have a custom coordinate system, I normally just modify an existing .prj file and then import that projection file back into ArcGIS Pro. It has always worked for me that way. I normally modify the .prj file in Notepad or some simple text editor.

Can you export your modified projection into a prj file, edit it, and then import it again?

tagging:

https://community.esri.com/groups/coordinate-reference-systems?sr=search&searchId=060d2ed0-8468-4278-8910-4f30620054ba&searchIndex=0‌

https://community.esri.com/groups/map-projections?sr=search&searchId=e3a3f09b-399f-4ed1-b710-5f90e21d26e2&searchIndex=1‌

Re: Modified projection failing to draw

DanPatterson_Retired — Wed, 31 Jan 2018 22:02:11 GMT

Does the modified file show up when it is added to a new map frame without anything else in it? Like no basemap... just plain blank (try it arcmap if it is still around as well)

Re: Modified projection failing to draw

AmyRock1 — Thu, 01 Feb 2018 21:21:26 GMT

Haven't tried that, as this is a pretty basic cartography course, so we typically have students just modify within ArcMap/ArcPro. To be clear, this isn't reprojecting a data layer, just setting the CS for a Map.

Re: Modified projection failing to draw

AmyRock1 — Thu, 01 Feb 2018 21:25:35 GMT

It has always worked just fine in ArcMap, but we have moved to Pro for this course this term. Same problem occurs when starting with a blank map, although even if I set preferences to start with no basemap, it still sets the initial map frame as Web Mercator, so "plain blank" isn't what it used to be.

Re: Modified projection failing to draw

DanPatterson_Retired — Thu, 01 Feb 2018 21:30:06 GMT

Yes... you can within the Project, Options section actually set your preferred coordinate system

A picture .... click on the Project top left to get to the preferences for projects... the options, Map and Scene and scroll-away

Re: Modified projection failing to draw

MelitaKennedy — Fri, 02 Feb 2018 00:11:22 GMT

This is a bug. It's fixed in 2.1. Note the additional parameter that showed up:

Scale Factor 0.0

Oops! Change this to 1.0, and the coordinate system will work properly.

Melita

tl;dr; AKA Geeky explanation:

Esri's Lambert conformal conic (LCC) algorithm is "overloaded" to support two variants. One variant uses two standard parallels (plus a latitude of origin). The other variant uses a latitude of origin and scale factor plus one standard parallel. The latitude of origin and standard parallel 1 need to be equal. Similarly, if you end up with standard parallel 2 in the definition it also needs to equal SP1 and lat of origin in this second variant.

For the already defined projected coordinate systems that use LCC, we only show the appropriate parameters. When you create a custom one from scratch or modify an exsting one, we don't know which variant you want so you get all the parameters. In this case, we weren't setting the scale factor parameter to the correct default of 1.0.

Re: Modified projection failing to draw

AmyRock1 — Mon, 26 Feb 2018 21:09:43 GMT

Awesome, thanks! In academic lab environments we aren't able to update to new versions immediately on release, so we'll soldier on with the correction.